This invention is related to tools used for removing and replacing valves which are in a system that must remain pressurized. The tool of this invention is designed for use on wellhead assemblies to remove wing valves from the side of the casing bowl or spool assembly and also to remove and replace master valves. The tool includes a packing assembly that is temporarily securable to a wellhead so the valve can be removed while the remainder of the system is pressurized.
One device is known in the prior art for removing wing valves and the like from a wellhead assembly, such is shown in U.S. Pat. No. 2,250,244 issued July 12, 1941 to J. R. Yancey. This device has a threaded portion in the bore of the wellhead and a threaded plug which is inserted through the valve by a suitable manipulator and screwed into the threaded portion to seal the fluid flow into the valve. While this scheme may function well on new equipment, the threaded portion of the bore will obviously be deteriorated by abrasive crude oil flowing through the conduit after a period of time. Deterioration of this threaded portion of the bore will render this type of tool unusable or at most unsafe considering the high pressures often encountered in wellhead assemblies.
Other devices are known in the art for plugging pipes so that valves can be installed directly in the flowline or joined transverse to the flowline by a flange. Two of these devices are shown in U.S. Pat. No. 2,780,224 to H. J. Lee issued Feb. 5, 1957 and U.S. Pat. No. 3,170,226 to T. A. Larry issued Feb. 23, 1965. The patent of M. M. Raspante, U.S. Pat. No. 3,275,023 issued Sept. 27, 1966 discloses a device for removing valves from large diameter water tanks and the like where the inside of the tank is relatively flat. None of these valve removal tools are particularly adapted for use on wellheads where high pressures (up to 30,000 pounds per square inch) and high temperatures (up to 1,500 degrees F.) may be encountered.